The present invention relates in general to acoustic imaging of regions within the body of a living being and more particularly concerns apparatus and techniques combining advantageous features typical of guidewires and ultrasound imaging probes.
Some of the features needed for a commercially practical design of such imaging devices are a construction that enables it to be conveniently made in a range of small sizes down to very small size, a distal end which can exert a degree of distal thrust to access parts of the body easily, and a tip which is non-traumatic so that it does not enter delicate linings of blood vessels or other ducts of the body.
It is also desirable for many such devices that their transducers not only be capable of high frequencies as used in existing ultrasound imaging catheters and guidewires but also for much higher frequencies, e.g. for closer imaging.
Ultrasonic imaging devices should also have usual guidewire-like qualities or catheter-like qualities, for instance variable stiffness along their length. A more flexible distal portion enables access to difficult-to-access regions of the body, while a stiffer proximal region of the catheter or guidewire enables pushing and manipulation. For instance, when imaging the coronary arteries, it is desirable to readily place a device in the femoral artery through a coronary guiding catheter, around the aortic arch and into the coronary ostium. Generally the guiding catheter only extends up to but not into the coronary ostium. With an appropriate design of an ultrasound device, with a very flexible distal portion, it becomes possible to exert good control over the imaging tip that is placed directly from the coronary ostium into the more distal region of the coronary artery.
It is also desirable to provide an ultrasound imaging device which is immediately usable rather than having to prepare a device specially by injection of water or saline or other fluid acoustic coupling medium.
It has been known to employ an acoustic imaging catheter which has the additional capability of fluid and drug delivery. It is desirable to achieve ways of doing this with improved or different versions of catheters that are produced to better fulfill the needs of physicians.
It has been known to apply thin lubricous coatings to guidewires and catheter devices to aid in deployment of the guidewire or catheter device and to protect bodily passages from abrasion during insertion and rotation of the guidewire or catheter device. Such thin lubricous coatings are described in Sahatjian et al., U.S. Pat. No. 5,135,516 and Sahatjian, U.S. Pat. No. 5,304,121, the entire disclosures of which are hereby incorporated by reference herein.
With prior designs, it has not been feasible to achieve all desirable combinations of the above features.